MDI Biological Laboratory seeks NIDDK R25 support for the ninth through thirteenth annual offerings of a one- week course for renal fellows, Origins of Renal Physiology. The course will be held the first week of September 2017 through 2021 on the MDI Biological Laboratory campus, in Bar Harbor, Maine. The proposed course provides renal fellows with hands-on research education in fundamental concepts of homeostasis and exposes them to the classical experiments that form the foundation of renal physiology and nephrology. Seven course modules are proposed: glomerular filtration, proximal tubule function, thick ascending limb cotransporters, salt secretion and balance, collecting duct sodium transport /ENaC, water homeostasis, and acid/base homeostasis. Each of the seven modules runs in three consecutive two-day rotations (Monday-Tuesday, Wednesday-Thursday, and Friday-Saturday), with the first day of each rotation involving intensive experimental work, and the second day involving analysis and presentation of the work to the entire course group. Each participant will complete three of the six planned modules during the three rotations. A case study-based Responsible Conduct in Research program will precede each rotation. Origins of Renal Physiology is entirely unique among national renal short courses. The course provides participants with research tools that give them a deeper understanding of concepts of physiological homeostasis which is difficult to attain during normal clinical training schedules. The course is open to renal fellows and, since 2010, on a space-available basis, medical residents entering nephrology. Fellows and residents alike benefit from close interactions with senior investigators in renal physiology who lead the course modules. Residents, in particular, benefit by working with fellows from different programs and sharing their insights into renal research and nephrology. The course is described on the MDI Biological Laboratory website (http://www.mdibl.org), and in a recent editorial in J. Am. Soc. of Nephrology (Zeidel et al., JASN 19: 649-50, 2008). Requested funds will cover course tuition and participant travel; faculty subsistence, stipends, and travel; facility user fees; consultant services; and personnel costs required to administer the research education program.